Process of reproducing natural wood finishes on metal and other surfaces



Patented July 19, 1932 UNITED STATES.

PATENT; OFFICE EMIL LOETSCHER, OF D U B UQUE, IOWA PROCESS orREPRODUCING NATURAL woon FINISHES N METAL AND OTHER suaraons a NoDrawing. Application filed April 28,

This invention relates to improvements in processes'for reproducingnatural wood finishes on surfaces of materials such as metal or otherwood substitute, and more particularly to improvements in thephotogravure process of ornamentation by reproduction of natural woodfinishes, which heretofore has included as the initial step that ofphotographing by means of a camera, the surface marking of a selectedpiece or panel of natural wood, and preparing the printing plates fromthe photographic negative.

The present process eliminates entirely the use of a camera as themedium for producing a photographic negative of a wood surface, but usesa thin sheet or veneer of the actual wood as the negative, and by takinga direct contact print onto sensitized paper to thereby produce apositive from which the printing plate is prepared.

' Although this so-called photographic method of wood grain reproductionon metallic or other finished surfaces has been extensively employed,itis not altogether satisfactory, the chief objection being the fact thatit is impossible to reproduce the natural efiect of the graining, sinceit is necessary to enlarge the grain and texture of the original subjectand to otherwise treat its surface in order to bring out the desiredefiect and detail.

It is readily apparent that a wood surface, no matter how beautifullygrained, is not a perfect photographic subject, for the reason thatthere is not a pronounced contrast between the background or foundationcolor and the graining, which is usually but a shade or so darker thanthe body of the wood. It is generally true, also, that the morebeautiful surface efiects are those in which the contrast is leastpronounced. Consequently, in reproducing a natural wood surface,byphotographing it by means of a camera, a considerable portion of thesurface detail is lost in the transmission from 1930. Serial No.448,160.

subject to plate due to absorption and loss of the reflected light fromthe subject in passing through the lenses of the camera. Consequently,it becomes necessary to stain the wood and to enlarge the texture of thegraining in order to bring out the desired contrast, and this, ofcourse, results in an unnatural reproduction and one which tends towarda coarse and unfinished effect.

natural and perfect reproduction of grained wood, however, can besuccessfully and economically obtained by the improved process, whicheliminates the use of a camera entirely, as a means of obtaining apositive print of the subject, but rather utilizes a very thin andtherefore translucent sheet or veneer of the actual wood to bereproduced as a negative, and by taking a direct contact print onto asheet of sensitized paper, this, when developed, becomes the positive 6from which the printing plates are prepared. The details of the processwill be understood from the following:

The particular wood which is to be reproduced isobtained in the form ofone or several thin sheets of veneer of the desired area, and which isreadily obtainable in commercial "thicknesses of from 1/80 to 1/ 100 ofan inch.

This thin sheet of veneer is then applied in direct contact with a sheetof sensitized paper of any suitable commercial grade. and finish andthen exposed to sunlight or artificial 'light until the desired degreeof exposure is obtained. The sheet is-then developed by the usualprocess and becomes the positive from which the halftone or rotogravureplates are made, depending on the'process to be followed. In short, thepresent improvement contemplates only the production of the positive bya direct contact print, using a thin veneer as a negative instead of thecustomary method of photographing the surface of a piece of natural woodand developing the negative.

The veneer being very thin is translucent and, therefore, it is possibleto print directly through the material reproducing every minute detailof pore and fibre in'its natural size and without exaggeration orresorting to other treatment in order to reproduce wit some degree ofaccuracy the original subject. Some care has to be exercised in carryingout the printing in order to obtain the proper exposure, but this can bereadily acquired with a little practice and experience. It isparticularly essential that close contact be maintained between theveneer sheet and the printing paper, so that the print will not beblurred where there is' a slight separation of the two. This is readilyaccomplished, however, by using a so-called vacuum printing frame wellknown in the photographic art, which makes it possible to hold thesheets in close contact during the printing operation.

After the direct contact print has been made, it is developed and dried,and becomes the positive from which a halftone plate or rotogravurecylinder is prepared in accordan'ce with the standard practice. Thushaving prepared the positive by the method of direct contact printing,the process followed from that point on depends on the nature of thework to be accomplished. For instance, if a panel of somecompositematerial is to be finished in imitation of a natural woodfinish, the rotogravure process would preferably be used, theimpressions being made on sheets of paper colored to give the properfoundation or base color of the wood. The sheets would then be treatedwith bakelite or other resinous varnish to give a hard andwear-resisting surface to the panel when the sheets are applied.Reproductions on paper for use as book covers may be made from halftoneplates, and impressions of natural wood finishes may be applied to metalsurfaces by the so-called offset process, using rolls for transferringthe pigment from the plates to the metal, as in the present practice.

Although no claim is made to any of the steps in the process ofreproducing natural wood finishes on surfaces other than the making ofthe positive by a direct contact print from thin sheets of veneer, thereare nevertheless distinct advantages in using the direct contact methodaside from obtaining accurate and natural reproductions of the subjectin the positive. 7

Take for instance the rotogravure method of printing in which thepositive print of the original subject is photographed through arotogravure screen and then transferred to the rotogravure cylinder by aphoto-engraving process. Where the nature of the work requires that thegrain extend continuously around the cylinder, it is quite difficult totransfer the impression onto the cylinder by the usual photographicmethod so that the ain will match at the meeting edges of theimpression, and hence it is necessary to resort to considerabledoctoring in order that the irregularity will not be visible when theimpressions are made. direct contact print method, however, this isavoided because the veneer sheets are so thin that numerous sheets maybe taken from the same log or block of wood, and each sheet will havepractically the same arrangement of graining as the adjacent-sheet. Itfollows, therefore, that two successive sheets of veneer when laid endto end, but with one reversed or turned over with respect to the other,the graining at their abutting ends will match without showing anappreciable break or joint. Thus, if a contact print is made of a sizeto correspond to the area of the rotogravure cylinder, the impressioneventually transferred to its surface will show no appreciable breakorjoint in the graining, so that the cylinder will print a continuousover- VVith the so-called all design without a visible mark orirregu- 1. In a process for re roducing natural wood finishes onsurfaces, t e steps of producing a positive print by direct contactprint of a sheet of natural wood veneer of such thinness as to transmitlight therethrough, and making a printing plate from said print.

2. In the photogravure process of reproducing natural wood finishes onsurfaces, the initial step of preparing a positive from a direct contactprint of a thin sheet of the natural wood to be reproduced upon a sheetof sensitized paper, said sheet of wood bein of such thinness as totransmit light there'- through. I

3. In a process of reproducing natural wood finishes on base materials,the steps of preparing a translucent sheet of thin veneer of the wood tobe reproduced, making a direct contact print of said veneer on a sheetof sensitized'printing paper, and transferring the subject of said printonto a metal printing plate by a photo engraving process. 4. In aphotogravure process for reproducing natural wood finishes on basematerials, the steps of preparing successive layers of veneer of thewood to be reproduced, said layers being in the form of thin translucentsheets, arranging said layers of'veneer and producing a printing platefrom said print. n

5. In the rotogravure process of reproducing natural wood finishes onbase materials, the steps consisting of preparing a plurality of thintranslucent sheets of veneer from a block of the wood to be reproduced,arranging said sheets edge to edge so that graining matches at theedges, exposing said veneer sheets to light in direct contact with asheet of sensitized printing paper, and transferring the resulting printto a rotogravure cylinder for continuous printing.

Signed at Dubuque, 1a., this 25 day of April, 1930.

EMIL 0. LOETSCHER.

